Phone in for charging issues, gets water damage

I took the cellphone into Foschini on 15 December 2014 for repairs as the phone struggled to charge.They took the phone and said it would take 4-6weeks as they need to send it to MTN. I went back end of January and they just said they had not received anything back, went back again a week and a half later when they only realised that day that the phone was never even sent for repairs. Kindly they borrowed me a phone until they got mine back, now they call and tell me that the phone has water damage which they do not repair. When I took the phone in on 15-12-2014 it was a month in my possession and wasn't even used that long, how can it have water damage if I didn't even use it for a month? My warranty is still valid so the insurance won't pay. I need to know what Foschini expects from their clients if this is the service they provide...